To facilitate processing of most resin compositions (e.g. acrylonitrile-butadiene-styrene resins, polystyrene resins, polyamide resins and polyvinylchloride (PVC) resins) lubricants are required if useful and uniform finished products are to be obtained. Lubricants paly a particularly important role in the extrusion, injection molding and blow molding of rigid PVC resin compositions.
Both internal and external lubrication is essential to maintain acceptable flow characteristics and rheological properties of the melt throughout the processing and to obtain a useful finished product. Internal lubrication operates within the melt to reduce the melt viscosity of the polymer at the processing temperature and improve the flow characteristics of the materials so that a high output is possible using a minimum amount of work and without destroying (degrading) the physical properties of the resin. External lubrication is required to reduce friction and sticking at the interface between the plastic melt and the metal surfaces of the processing equipment in order to obtain a consistently uniform product having a smooth finish and essentially free of surface defects.
Emphasis has recently been shifted to developing new and better lubricant compounds which meet all the lubrication requirements for processing PVC and other resins, that is, function both as internal and external lubricants. Several commercially available ester and ester-soap waxes derived from montanic acids are recommended for this purpose. Montan wax acids are mixed monocarboxylic acids obtained from lignite and typically contain from about 22 to 35 carbon atoms with the predominant acids falling in the C.sub.26 -C.sub.32 range. The bulk of the monocarboxylic acids derived from montan wax are aliphatic straight-chain acids having an even number of carbon atoms.